Summary of Work: Current methods of determining global ventricular function depend on planar cardiac imaging techniques. In these techniques, activity in front of and behind the heart are superimposed upon left ventricular bloodpool activity. In addition, physical constraints prevent images from being acquired along the true long axis of the left ventricle. Recent developments in gated single photon emission computed tomography imaging have shown that it is possible, in approximately the same imaging time, to acquire fully three-dimensional images of the beating heart, and thus of ventricular function. In addition, recent developments in imaging technology have shown that ventricular function may be determined from gated perfusion or metabolism tomographic images. This project set out to determine the accuracy and feasibility of making such quantitative measurements. The first phase of the project (now complete) focused on gated blood pool (GBP) studies and found that, by "reprojection" of the data into a true long axis planar slice, one could produce ejection fraction (EF) results that were both more accurate and potentially more reproducible than existing EF techniques. This finding is expected to have a significant impact on clinical studies (e.g., Q9 evaluation of adriamycin therapy) in which clinical decisions are based on small changes in EF over time. These results have recently been published. The second phase of this project is now beginning; namely, to use the tomographic data directly to compute regional, rather than simply global, function. This would permit direct correlation of regional function with perfusion or metabolism.